Use -O0 for ppc64le, otherwise the test suite fails.

diff -up ck-0.6.0/build/ck.build.ppc64.o0 ck-0.6.0/build/ck.build.ppc64
--- ck-0.6.0/build/ck.build.ppc64.o0	2018-07-17 08:37:07.950979938 +0200
+++ ck-0.6.0/build/ck.build.ppc64	2018-07-17 08:36:05.080532259 +0200
@@ -1,2 +1,2 @@
-CFLAGS+=-m64 -D__ppc64__
+CFLAGS+=-m64 -D__ppc64__ -O0
 LDFLAGS+=-m64